Ensuring only one db-migration-rds job runs at once
Ensuring only one db-migration-rds job runs at once

[finishes #157760939](https://www.pivotaltracker.com/story/show/157760939)

Co-authored-by: Max Becker <e6d855fe2263fd0035edb7e1f665a7466a1b4c9c@sap.com>

barthy1/bosh,barthy1/bosh,barthy1/bosh,barthy1/bosh